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The Effect of Salinity on the Rate of Dolomitization

Martin, Stephanie L.; Cudnik, Brittney; DeMille, John; Montoya, Chris; Barrie, Edward; Kaczmarek, Stephen E.

Dolomitization of limestone is a complicated diagenetic process that is affected by a number of thermodynamic and kinetic factors as demonstrated by field and laboratory observations. Among these are temperature, mineralogy and grain size of the precursor limestone, Mg/Ca ratio of the solution, and a host of kinetic inhibitors. Some research suggests that salinity levels may also affect the rate at which dolomite replaces CaCO3. Here we use geochemical modeling and high-temperature dolomite replacement experiments to test the effect of salinity (i.e., NaCl concentrations) on dolomite formation. The results of these two approaches are consistent and indicate that dolomite growth is slower in fluids with higher salinity concentrations. These results are interesting in that one of the most implicated models of dolomite formation in nature, the refluxing brine model, is based on the idea that concentrated brines (i.e., fluids of elevated salinity) act as the primary dolomitizing agent. These results suggest that lower salinity fluids may dolomitize limestone more efficiently than concentrated fluids.


AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013